Activity monitoring device

ABSTRACT

A device for monitoring the activity of a user to prevent deep vein thrombosis when travelling on transportation vehicles. The device comprises a carrier ( 20 ) for positioning on or adjacent a user, a motion sensor ( 10 ) mounted on the carrier ( 20 ) and adapted to detect the user performing a predefined motion, processor adapted to filter the motion detected to remove background motion not attributable to the desired exercise and to reset a timer ( 12 ) when the predefined motion is detected. An alarm ( 14 ) is operated by the processor should the time period elapse without the exercise pattern being detected. The components are all contained in the carrier ( 20 ) which is preferably a small container that can be attached to a user&#39;s trousers or around the limb of a wearer. Failure to undertake the required motion will cause the alarm ( 14 ) to be activated, thus notifying the wearer of the omission.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. Ser. No.10/474,892, filed Oct. 10, 2003, which is the national stage (under 35U.S.C. 371) of International Application No. PCT/GB01/05136, filed Nov.21, 2001.

BACKGROUND OF THE INVENTION

This invention relates to a device for monitoring the activity of aperson travelling on a transportation vehicle and notifying that personof a specified pattern and frequency of their activity or inactivity, inorder to reduce the risk of them developing deep vein thrombosis.

The present invention finds a particular use in the prevention of deepvein thrombosis (DVT), which is often caused by extended periods ofinactivity, and it will be primarily described with reference thereto.

Deep vein thrombosis is a condition resulting from the lack of bloodflow in the veins and the condition is related primarily, but notexclusively, to the legs. Blood flow tends to slow down or stop whenthere is prolonged inactivity, especially when seated, as would happenon a plane or any long journey in a cramped space. More specificallydeep vein thrombosis occurs when a clot forms in the deep veins withinthe calf or thigh muscles. It is usually a spontaneous condition thatoccurs in people especially at risk, such as those with heart disease,those who smoke or consume alcohol and those that are generallyoverweight.

Any period of prolonged inactivity can generally trigger the conditionand medical research suggests that those over forty years of age are atever increasing risk. Warning signs are pain and tenderness in the legmuscles, redness and swelling of the skin. If the blood clot moves tothe lung (a pulmonary embolus), then breathing difficulties can occur. Aclot travelling on to the heart can cause death or if it travels to thebrain a stroke is a possibility. There are well-documented cases ofpeople suffering from this condition during long haul plane journeys andthere have been some deaths attributed to DVT. In recent times a numberof airline passengers have taken legal action against airline companiesrelating to this condition, and some companies are now putting warningson their tickets.

The more cramped the condition, such as would occur in the economy classarea of a plane, the more likely a person is to suffer from DVT, butrecent medical research shows that the condition can occur to any classof traveller who does insufficient exercise.

It is to be expected that on a long haul flight lasting several hoursthat people will sleep for extended periods of this time. This cannot beprevented on an individual basis and this is where a problem may arise.Furthermore, due to the cramped conditions, people may at other times,for one reason or another remain essentially motionless. This inactivityreduces the blood flow in the legs and the potential problem of DVTbecomes a factor.

Regular use of the legs during a journey dramatically reduces the riskof DVT. However, the transportation operators have no way of ensuringthat suitable exercise is done by their passengers, despite the factthat the health and safety of those passengers is at least partially theairline operator's responsibility. The problem of DVT is not limited toairline travel, but is also encountered in other forms of transport suchas cars, coaches and trains wherein prolonged periods of sedentaryinactivity occur, usually in confined areas.

At present, the onus may be on travel operators to ensure that theirpassengers do not get DVT. However, the present type of traveller onlong haul flights will clearly fit many of the conditions associatedwith DVT and as such can expose the travel operators to significant riskof negligence claims.

Previous attempts have been made to monitor the movement of patientssuch as those described in U.S. Pat. No. 5,941,836, U.S. Pat. No.6,646,556, U.S. Pat. No. 4,536,755, U.S. Pat. No. 5,523,742, U.S. Pat.No. 4,064,368 and U.S. Pat. No. 6,445,298. None of these are designedfor or suitable for use by passengers on transportation vehicles becausethey are large, cumbersome, suitable only for lying down and/or unableto distinguish relevant exercise movement from background movementcaused by incorrect activity or the motion of the transportationvehicle.

BRIEF SUMMARY OF THE INVENTION

The present invention aims to provide a mechanism by which the motion orlack of motion of a person may be monitored and remedial action taken ifthe exercise is deemed inappropriate. In the context of DVT preventionit aims to reduce the risk of DVT occurring and move responsibility fromthe travel operators to the individual passenger by providing them witha device that will warn of lack of sufficient and suitablemovement/exercise of the limbs.

The invention aims to provide a device that detects a deficiency in atraveller's exercise regime; alerts the traveller to the increased riskof DVT and promotes the appropriate exercise regime. To find utility ina transport setting the present invention provides a device that issmall and portable enough to be used in a travel setting withoutcompromising the comfort and safety of the travellers; that can detect aspecific exercise in a vibration rich environment; can learn theappropriate exercise habits of an individual, calculate, andautomatically adapt to reduce an individual traveller's risk; and isable to adjust its ability to detect exercise as the environmentchanges.

According to the present invention there is provided a transportationvehicle passenger activity monitoring device for monitoring the activityof a user travelling on a transportation vehicle, the device comprisinga carrier adapted for releasable attachment to a user, a motion sensormounted on the carrier to detect motion of the user; a processor alsomounted on the carrier that receives motion information from the motionsensor and which differentiates motion attributable to the userperforming a defined exercise from the overall pattern of motiondetected, and an alarm adapted to be triggered should a time periodelapse without the motion attributable to the user performing thedefined exercise being detected, wherein the defined exercise and timeperiod are such that the alarm is triggered if the user does notcorrectly exercised sufficiently frequently to reduce the risk of deepvein thrombosis, and wherein all of the components of the device areself contained on the user such that the device is portable within atransportation vehicle.

The processor may include a timer adapted to count the time period, andbe reset if the user correctly performs the defined exercise. The timermay be a separate component linked to the processor.

The type of motion sensor used is important, and it is highly preferredthat the motion sensor comprises a movable contact head mounted on ashaft, and contact plates at right angles to each other and adjacent thecontact head to detect movement radially with respect to the shaft bycontact of the head with the contact plates. The motion sensor may alsoinclude a calibration actuator that is in contact with the shaft and isable to detect vibrations and provide this data to the processor andwhich may also under control of the processor adjust the motion of thecontact head. This can be used to minimise the effect of backgroundvibrations. The calibration actuator may be linked to the processor todynamically adjust the motion of the contact head to minimise the effectof background motion such as that caused by the transportation vehicle.

A small, discrete, self contained device is essential as it must be wornby a user without causing discomfort or danger. Therefore it ispreferred that the carrier includes a shell within which the processor,motion sensor and alarm are mounted. This shell should also house allother components such as a power source.

The processor may preferably include a computer memory and softwareadapted to perform an analysis of data received from the motion sensorto differentiate the motion attributable to the user performing thedefined exercise from the background motion. The software may be storedin the memory and run in the processor in several modes of operation.This may include: a learning mode in which specific performance of thedefined exercise is detected and used to calibrate the device tominimise background motion; and a normal mode during which thecalibrated device monitors the activity of the user on a journey.

The device may be further provided with a user interface to provideinformation to the user and/or to allow input by the user of informationin to the device. Such user inputted information may include informationselected from the group consisting of the user's height, the user'sweight, the user's age and the user's lifestyle.

The device may be used to compliment other types of DVT preventionequipment. It is known to use an air bag exercise apparatus which can beused by a seated person to reduce risk of developing DVT. This apparatusrelies on the user to undertake the exercise and so does not ensure thatthey are reminded to do so. The present invention also provides anexercise apparatus provided with an activity monitoring device aspreviously described which is adapted to monitor the correct use of theexercise apparatus and sound the alarm if insufficient or incorrect useis made of the apparatus. The apparatus could be a two chamberinflatable device, and this could also be provided with a pump forinflation thereof.

The device can monitor the activity of the entire body or of a specificlimb and in order to monitor such activity it is essential that thesensor be positioned so that it may detect the movements of one or morepart of the body. It is preferred that the sensor is held against theuser and more particularly the limb of a user, and so the carrier mayinclude an attachment means to permit removable attachment of the deviceto a user. Those attachment means may take any suitable form, but forattachment to a limb, they may comprise a strap that is adapted to passaround that limb. Such a strap may be made such that it may be stretchedto pass over the hand or foot and then grip the limb once fastened.Alternatively the strap may be in two parts, the free end of each partbeing provided with means for inter-attachment, such as a two part hookand loop fastener (for example those sold under the trade name Velcro®),or a buckle. Releasable adhesive could also be used to fix the device toa limb or clothing. Ideally the device should be as small and easy toattach to the user as possible, it is therefore preferred that thecarrier includes a mechanism for the releasable attachment to the useror the user 's clothes. A catch or pin to engage the user's belt orclothes is highly suitable.

The motion sensor must be adapted to discern various patterns ofmovement characteristic of the defined exercise routine, from othermotion that is either caused by the transportation vehicle or by theuser. This allows the device to discern between different types ofactivity and only to record the performance of correct activity. Thisprevents the suppression of the alarm by insufficient or inappropriatemovement.

Vibration can be classified into one or more of the followingcategories: periodic, random, resonant and harmonic. A periodicvibration repeats itself once every time period. In real terms dorsi andplantar flexion (which are suitable exercise motions) cause such onceper cycle vibration which is periodic by nature. Random vibrations donot repeat themselves, and are not related to a fundamental frequency.An example in a plane might be hitting an air pocket, or in a car goingover a pot hole.

Resonant vibrations occur at the natural frequency at which an airframeor mechanical system is inclined to vibrate. All things have one or moreresonant frequency. Resonant vibrations are the result of a response ina mechanical system to a periodic driving force. Harmonic vibrations areexact multiples of a fundamental frequency.

The type of exercise motion that the motion sensor is adapted to monitormay be preset during manufacture, as may the time period for itscompletion. Such manufacture settings could adapt the device to aparticular type of use (e.g. plane as compared to car) or user (e.g.overweight as compared to ideal weight). Alternatively, the type ofpredetermined motion and indeed the preset time period may be adjustedto allow the device to be swapped between different uses. Thisadjustment may be conducted by reprogramming the devices betweendifferent modes, using controls on the device or by control remotelyfrom the device. The device may also be adapted to permit userinterface, so that characteristics of the user, the transportationvehicle and the user's lifestyle can be input directly into the deviceto determine the required form, duration and frequency of exercise.

The alarm must be able to notify the user, and possibly persons otherthan the user, of the correct or incorrect activity, and may therefore,dependant on the end use, take several different forms. The alarm mayinclude at least one of an audible signal generator such as a speaker, alight source such as a flashing LED, a vibrator such as is used inmobile phones and a transmitter connected to a remote notificationsystem. Such a transmitter might be used when it is additionally, oralternatively, desired to notify a person other than the user (wearer)of the device.

Means for transmitting and/or receiving data may be included, either aspart of the alarm, or in addition to the alarm, and these can allowremote control and monitoring of the device.

The device may be adapted for attachment to a person who desires tocorrectly carry out a specific exercise. In such an embodiment, the typeof predetermined motion may be set to the pattern generated by thecorrect completion of the specific exercise routine, and the preset timeperiod of the timer is set so that the alarm is triggered if theexercise is not correctly performed at the required frequency by theperson wearing the device.

In a more sophisticated version of the invention the following sequencehappens. A wearer will be given an alert on activation of the device.The alert might comprise the flashing of the LED, a buzz from avibration motor or a message on a screen. The microprocessor could allowfor the LED to flash in time with an exact exercise being achieved, inso doing it could train the wearer to do a specific regime of exercise.The LED will flash every fifteen seconds to show its wearer that it isfunctioning correctly.

In a further use of the LED, it could be that should the wearer refuseor fail to do the exercise in any one or more period of monitoring, thenthe flash rate of the LED could be changed by the processor to twoflashes every fifteen seconds to indicate this. This has the function ofalerting the crew of the transportation vehicle that the wearer refusedor failed to do the determined exercise regime recommended.

The device would include a timer that can monitor activity over asuitable period such as fifty to sixty minutes and ifinsufficient/inappropriate exercise is detected in that period then itwill cause a warning, such as three distinct buzzes of the vibrationmotor to warn a user to do the exercise regime.

On completion of the exercise another signal can be sent to the wearer,e.g. via the vibration motor, to indicate to the wearer that they canstop doing exercise. The device could then reset its clock and continueto monitor for a further fifty or sixty minutes.

According to the present invention there is also provided a method ofpreventing deep vein thrombosis in a passenger travelling on a journeyin a transportation vehicle, the method comprising:

-   -   providing the passenger with a self contained activity        monitoring device comprising a motion sensor to detect motion of        the passenger; a processor that receives motion information from        the motion sensor, and an alarm, the activity monitoring device        being mounted on the passenger during the journey;    -   defining, on the basis of characteristics of the passenger, an        exercise pattern to be performed, including a frequency time        period for its repetition, to reduce the risk of deep vein        thrombosis;    -   processing in the processor the motion detected by the motion        sensor during the journey to differentiate motion attributable        to the user performing the defined exercise pattern from the        overall pattern of motion detected including the background        motion caused by the transportation vehicle; and    -   notifying the passenger, by means of the alarm, if insufficient        or incorrect exercise is detected in order that the defined        exercise pattern may be performed to reduce the risk of deep        vein thrombosis.

The step of defining the exercise pattern may include the inputting into the device by the passenger of information concerning their lifestyleand body characteristics (age, height, weight etc). This can be used todefine a risk profile and so to determine an appropriate exercisepattern.

After the step of defining the exercise pattern, there may be a furtherstep of placing the device in a calibration mode during which thepassenger performs the defined exercise pattern (possibly but notessentially with minimal background motion). The particular vibrationprofile associated with the performance of the exercise by the passengeris detected and stored for use during the journey when the device is notin the calibration mode.

At least the step of processing the detected motion is preferablycarried out by software stored in the device and running on theprocessor. This processing is at least a two stage process. The firststage filters the detected motion and dynamically calibrates the sensorto minimise background effects. This feeds motion information that iswholly or predominantly attributable to the activity of the user throughto the second stage. The second stage analyses this motion forcompliance with the defined exercise pattern in the time period. If thisis detected the user is not notified, but if suitable activity is notdetected the alarm may be triggered.

According to the present invention there is yet further provided adevice for monitoring the activity of a user travelling on atransportation vehicle, the device comprising a carrier adapted forlocal attachment on or adjacent a user's leg by means of a releasableattachment device, a motion sensor mounted on the carrier and adapted todetect the user performing a predefined pattern of movement over apreset time frame, a timer mounted on the carrier and connected to themotion sensor so as to be reset should the motion sensor detect thepredefined pattern of movement within the time frame, and an alarm alsomounted on the carrier and connected to the timer for triggeringthereby, should the timer count a preset time period without beingreset, wherein the predefined pattern movement and the preset time frameof the timer are such that the alarm is triggered if the limb of theuser is not correctly exercised sufficiently frequently to reduce therisk of deep vein thrombosis and wherein all of the components of thedevice are self contained on the user such that the device is portablewithin a transportation vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the present invention may be better understood, but by wayof example only, various embodiments of the present invention will nowbe described in more detail with reference to the following drawings, inwhich:

FIG. 1 is a simplified block schematic view of one embodiment of deviceaccording to the present invention;

FIG. 2 is a perspective view of further similar embodiment in a formready for use;

FIG. 3 is a simplified block schematic view of a further embodiment ofdevice wherein the alarm comprises a low power transmitter, incommunication with a remote monitoring station;

FIG. 4 is a flow chart to demonstrate operation of the embodiment ofFIG. 1;

FIG. 5 is an alternative more sophisticated embodiment of the invention;

FIG. 6 is a flow chart to demonstrate the embodiment of the embodimentof FIG. 5;

FIG. 7 is a simplified view of a motion suitable for use in the presentinvention; and

FIG. 8 is a flow chart to demonstrate the operation of a thirdembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a simple schematic view a first embodiment of the presentinvention. The device comprises a motion sensor 10 positioned so that itmay detect the movement of a user (not shown); a timer 12 connected tothe sensor 10 and an alarm 14. The timer counts down a time period froma preset time t to zero (or up from zero to t), and when it reaches theend it cause operation of the alarm through a controller 16. The timer12 and controller 16 are integrated within a processor 17. In thecontext of DVT prevention in airline passengers t may be 56 minutes. Themotion sensor is adapted to detect a motion and the processor 17discerns if the correct motion is detected and when it is detected, thetimer 12 is reset to t. A power source in the form of a battery 18powers the various components. The alarm may take several forms andindeed a device may include several different types in combination. Forexample a silent vibrating alert might be appropriate for a passenger ona plane to prevent annoyance to others.

A more practical embodiment of device operating essentially as describedwith reference to FIG. 1 is shown in FIG. 2. In this embodiment themotion sensor, battery and processor are housed inside a carrier 20which can be affixed to a wearer using the straps 22 and 24. The strapsare passed around the leg (if using for DVT prevention) of a user andconnected using a two part hook and loop fastener, one part of which 26can be seen on the inner face of the strap 24. The carrier 20 isprovided on its outer face 28 with an LED 30 which forms part of thealarm, and with an LCD screen 32 indicating operative information aboutthe device such as the time until activation of the alarm or the numberof alarm activations.

The device shown in FIG. 2 is intended for use by a passenger on a longjourney, such as a long-haul airline flight. The device could bestrapped to the ankle, leg or waist of a passenger using the straps 22and 24 and the predetermined motion and time period will be set so as todetect regular motion suitable to reduce the chance of the passengerdeveloping DVT. An example of appropriate exercise might be the tappingof the foot on the floor more than 180 taps in a 3 minute period tocause resetting of the timer. The length of the time period (t) that thetimer counts down can vary, but for the prevention of DVT the exercisemay comprise 180-240 foot taps in a three to four minutes period andrepeated at least every 30 minutes to 1 hour (t=30 to 60 minutes).Dorsiflexion suggests the aforementioned range of taps is sufficient asin use on post op rehabilitation.

As long as the wearer performs the correct exercise regularly enough thetimer will be reset and the alarm will not sound. Should correctmovement NOT be detected then the timer will reach zero and trigger thealarm, thereby reminding the passenger to make the necessary exercise.The time period and type of exercise can be set by medicalrecommendation and by the characteristics of the user including height,weight, age and lifestyle.

The device could also detect other types of exercise that meet thecriteria such as walking around and would also reset the counter inresponse to these. This minimises unnecessary activation of the alarmand prevents annoyance to the wearer. A range of devices could beprovided on a plane with different preset values. Devices with differentpreset values could be colour-coded to allow the crew to make adistinction between different types of people. For example, people whocould be at greater risk of DVT might be given a device with a shortertime period than those who are at less risk. It is envisaged that thesedevices with varying preset timing values could be distributed to thepassengers at the commencement of the flight. During pre-flight safetydemonstration their use could be described and demonstrated.

Simple embodiments of the device are automatic and require no adjustmentor button pressing from either staff or passengers, as once they arepreset the airline staff could literally hand them out in the same way,as for example, headphones are given out for onboard entertainment. Inmore advanced versions of the present invention the device can beadapted to define a suitable exercise pattern depending on theinformation provided by each user.

The LCD screen 32 could display the number of times the device has beenreset by exercise. This information could be logged by the airlinemanually or automatically and then correlated to the seat position andpassenger name. This would give the airline company a record of aparticular passenger's compliance with the recommended exercise regime.

In practice, each passenger could be given this device and requested towear it for their safety. Should they refuse or simply not use it thenthe airlines would have complied with the principle of providing as safeas possible a journey and the onus would shift on to the individualpassenger.

A small transmitter could be used in conjunction with the device andthis is shown in FIG. 3. The embodiment of device in FIG. 3 isessentially similar to that shown in FIG. 1 and therefore like partswill be given like reference numerals. The difference between the twoembodiments is that the alarm 36 in FIG. 3 includes a transmitter 36 inwireless communication with a receiver at a remote monitoring station38. In this way the alarm signal may be transmitted to a remote locationfor monitoring by a third party. The transmitter could use low powerradio waves or ultrasound to communicate with the remote monitoringstation.

FIG. 4 is a flow diagram showing a simplified version of how anembodiment of device might operate. The device is initially attached toa wearer and reset at stage 40. The timer then begins counting down atstep 41, whilst monitoring movement at step 42. If movement is detectedthe type of movement is analysed at step 43, and the movement associatedwith exercise is discerned from that attributable to background motion,and if it meets the criteria the timer is reset at stage 40. If thecorrect motion is not detected the timer reaches the end of the timeperiod at step 44, and the alarm is activated at step 45. The motionsensor continues to monitor for activity at step 46, and whilst none ofthe correct pattern is detected, the alarm continues to activate at step47. If exercise is detected, it is analysed at step 48, and if it meetsthe criteria the timer is reset at stage 40 to restart the cycle. If theexercise is not correct, the alarm will continue to be activated, unlessit is manually cancelled.

The embodiment in FIG. 5 comprises a microprocessor 49 on which driverelectronics are run, and to which is fed motion data from the sensor 10.The sensor also receives feed back calibration information from theprocessor. An alarm comprising a sounder/vibration motor 14 and an LED30 are driven by decisions made by software 51 running in themicroprocessor 49. The LED 30 is used to alert the user that the deviceis functioning properly and also to alert that exercise over at leastone period has not been carried out. This is achieved by changing of theLED flash pattern. A battery 50 provides power to the device.

The flow chart in FIG. 6 shows how the device in FIG. 5 might operate.

An embodiment of motion sensor suitable for the present invention isshown in FIG. 7. The sensor comprises a hammer 80 mounted on a base 82by location of a shaft 84 in an upstanding part 86. The hammer has aweighted metal contact 88, which when affected by vibration ofsignificant amplitude completes an electrical circuit with at least oneof a contact on the base 82 and a second contact 90 at ninety degrees tothe base contact. The hammer is mounted by the shaft 84 which isinsulated by an insulation sleeve 92 which covers the hammer shaft.

A solenoid controlled adjuster 94 is in contact with the hammer shaft84. This can be used to adjust the sensitivity of the sensor and totransfer minute hammer movement to a solenoid coil in an adjusteractuator 96. This provides feedback on resonant and harmonic vibrationsto the microprocessor, and the actuator 96 can be used to alter themotion of the hammer in response to the processor's control signals.

As mentioned above to use exercise to reduce the risk associated withDVT in a transport setting the present invention provides the followingunique combination of qualities: 1) portable enough to be used in atravel setting without compromising the comfort and safety of the useror fellow passengers; 2) detects a specific exercise in a vibration richenvironment; 3) can learn the appropriate exercise habits of anindividual, calculate, and automatically adjust the exercise regime toreduce an individual traveller's risk; and 4) can adjust its ability todetect exercise as the environment changes.

To ensure the present invention is portable enough to use in a travelsetting and not compromise the comfort and safety of the user and fellowpassengers, the important design factors are: power consumption,processor size, passive component size, battery size, sensor size, motorsize, and the manufacturing process.

The longest uninterrupted flight in regular schedule takes 18 hours, andthe present invention has been tested to run for more than two weekscontinuously using battery power. For present requirements, size nolonger determines processor power or speed. Because of recent advancesin chip design, microprocessors that meet our size, speed, and powerrequirements are readily available.

Battery size may preferably be approximately 23 mm diameter and 5.4 mmheight. The sensor measures 20 mm in length×6 mm width×16 mm deep. Thevibration actuator currently used is 16 mm length×6 mm in diameter. Themanufacturing process uses chip on board combined with surface mountcomponents.

An exercise detection flowchart is shown in FIG. 8. In normal mode,vibrations of the various types feed through the sensor 10. The sensor'scharacteristics tend to filter out the resonant and harmonic vibrations,leaving the exercise (periodic vibrations) and some of the randomportion of the vibration picture. This detected motion is feed into themicroprocessor 17, and stage 1 of detection software running on theprocessor filters this to remove the random portion. The result of thisclearly identifies whether the traveller is active or not and also howwell, the sensor is coping with the resonant and harmonic portion of thevibration picture. The software in the processor uses the solenoid coilin the actuator 96 to detect and isolate changes in the vibrationpicture which are then referenced against the exercise being performed.After the processor finishes polling the actuator 96 it uses the samecoil to drive the hammer adjuster 94 to adjust the sensitivity andcalibration of the sensor as necessary. This unique twofold use of theactuator allows it dynamically to adjust the sensitivity of the sensorto cope with environmental changes in real time.

The software has a second stage process that monitors the frequency ofthe detected movement and compares it with the traveller's definedexercise profile. The second stage also uses this profile to help filterout any random vibration with amplitude great enough to pass through thestage 1 filter.

The device has a training mode which allows it to learn the relevantexercise habits of an individual passenger and automatically to adjustthe exercise regime to reduce their DVT risk. During the initialtraining mode the passenger is asked to perform a series of movements.This data is then used to form part of the traveller's profile. In anadvanced embodiment the traveller can interact with the device through auser interface such as an LCD screen and buttons. This interactionallows the traveller to enter information that helps determine their DVTrisk. The software combines this with the other data to develop aprofile for the traveller, and thereby to adjust the defined exerciseregime appropriately.

The background motion caused on a transportation vehicle can alter ondifferent journeys or indeed during the same journey. The presentinvention can automatically adjust its ability to detect exercise as theenvironment changes. This is achieved this by using two-way interactivefeedback between the processor and the sensor (see FIG. 8). Asconditions change, feedback from the actuator allows the sensor to beautomatically adjusted which reduces the effects of background motion onthe sensor.

1. A transportation vehicle passenger activity monitoring device formonitoring the activity of a user travelling on a transportationvehicle, the device comprising a carrier adapted for releasableattachment to a user, a motion sensor mounted on the carrier to detectmotion of the user; a processor also mounted on the carrier thatreceives motion information from the motion sensor and whichdifferentiates motion attributable to the user performing a definedexercise from the overall pattern of motion detected, and an alarmadapted to be triggered should a time period elapse without the motionattributable to the user performing the defined exercise being detected,wherein the defined exercise and time period are such that the alarm istriggered if the user has not correctly exercised sufficientlyfrequently to reduce the risk of deep vein thrombosis, and wherein allof the components of the device are self contained on the user such thatthe device is portable within a transportation vehicle.
 2. A device asclaimed in claim 1 wherein the processor includes a timer adapted tocount the time period, and be reset if the user correctly performs thedefined exercise.
 3. A device as claimed in claim 1 wherein the motionsensor comprises a movable contact head mounted on a shaft, and contactplates at right angles to each other and adjacent the contact head todetect movement by contact of the head with the contact plates.
 4. Adevice as claimed in claim 3 wherein the motion sensor includes acalibration actuator that is in contact with the shaft and is able todetect vibrations and adjust the motion of the contact head.
 5. A deviceas claimed in claim 4 wherein the calibration actuator is linked to theprocessor and dynamically adjusts the motion of the contact head tominimise the effect of background motion such as that caused by thetransportation vehicle.
 6. A device as claimed in claim 1 wherein thecarrier includes a shell within which the processor, motion sensor andalarm are mounted.
 7. A device as claimed in claim 1, in which carrieris adapted for attachment to a user's clothes.
 8. A device as claimed inclaim 1, in which the defined exercise processor is adapted to detectand/or the time period may be adjusted.
 9. A device as claimed in claim1, in which the alarm includes at least one of an audible signalgenerator, a light source, and a vibrator.
 10. A device as claimed inclaim 1, in which the processor includes a computer memory and softwareadapted to perform an analysis of data received from the motion sensorto differentiate the motion attributable to the user performing thedefined exercise from the background motion.
 11. A device as claimed inclaim 10, in which the software running in the processor defines severalmodes of operation including: a learning mode in which specificperformance of the defined exercise is detected and used to calibratethe device to minimise background motion; and a normal mode during whichthe calibrated device monitors the activity of the user on a journey.12. A device as claimed in claim 1, in which there is further provided auser interface to provide information to the user and/or to allow inputby the user of information.
 13. A device as claimed in claim 12, whereinthe user interface allows input of information selected from the groupconsisting of the type of transportation vehicle, the user's height, theuser's weight, the user's age and the user's lifestyle.
 14. A device asclaimed in claim 1, which also includes means for transmitting dataconcerning the activity of the user.
 15. A device as claimed in claim 1,which also includes means for receiving data, such as data concerningthe user.
 16. A method of preventing deep vein thrombosis in a passengertravelling on a journey in a transportation vehicle, the methodcomprising: providing the passenger with a self contained activitymonitoring device comprising a motion sensor to detect motion of thepassenger; a processor that receives motion information from the motionsensor, and an alarm, the activity monitoring device being mounted onthe passenger during the journey; defining, on the basis ofcharacteristics of the passenger, an exercise pattern to be performed,including a frequency time period for its repetition, to reduce the riskof deep vein thrombosis; processing in the processor the motion detectedby the motion sensor during the journey to differentiate motionattributable to the user performing the defined exercise pattern fromthe overall pattern of motion detected including the background motioncaused by the transportation vehicle; and notifying the passenger, bymeans of the alarm, if insufficient or incorrect exercise is detected inorder that the defined exercise pattern may be performed to reduce therisk of deep vein thrombosis.
 17. A method as claimed in claim 16,wherein the step of defining the exercise pattern includes the inputtingin to the device by the passenger of information concerning theirlifestyle and body characteristics.
 18. A method as claimed in claim 16,wherein after the step of defining the exercise pattern, there is afurther steps of placing the device in a calibration mode whilst thepassenger performs the desired exercise pattern, detecting a particularvibration profile associated with the performance of the exercise by thepassenger and storing that detected pattern for use during the journeywhen the device is not in the calibration mode.